A common form of seed meter in widespread use is a pressure differential seed meter, either vacuum seed meter or positive pressure seed meter. The meter includes a housing having a rotatable seed singulating element therein, often a seed disk. On one side of the seed disk, the housing forms a reservoir to hold a pool of seed to be planted. The seed disk has an annular array of apertures through the disk near the disk periphery. An air pressure differential is created between the opposite sides of the disk. This can be the application of a positive pressure on the seed side of the disk or vacuum applied to the opposite side of the disk. When the disk is rotated, the pressure differential causes seed to be adhered to the apertures on the seed disk. The disk rotates to bring seeds, one at a time, in sequence to a release point where the seeds are discharged from the disk and moved sequentially to a furrow opened in the soil below.
The magnitude of the air pressure differential is usually controlled by the machine operator. If there is insufficient pressure differential, seeds will not always adhere to the disk resulting in what is referred to as “a skip” where there was no seed on a given aperture of the disk. Skips result in lost yield potential by a reduced number of seeds planted. Alternatively, too much pressure can result in two or more seeds being adhered to an aperture in the seed disk. This results in what is called “a double” or “multiple.” When two seeds are planted together, they compete for water and nutrients with the result being that both plants together do not produce as much as one properly planted plant. To avoid or at least reduce doubles, some form of mechanical seed removal is typically included in the seed meter, referred to as a “doubles eliminator” or in some instances, known as a “singulator” in that it produces single seeds on the apertures. In some instances, the seed disk is referred to as a “singulator” or “singulating element” as it removes seeds from the seed pool one at a time for deposit into the soil. The latter use of the term “singulator” or “singulating element” will be used herein.
Examples of doubles eliminators can be found in prior patents U.S. Pat. No. 7,699,009 to Sauder; U.S. Pat. No. 7,152,542 to Eben; U.S. Pat. No. 5,842,428 to Stefflebeam; and U.S. Pat. No. 5,170,909 to Lundie. One common aspect of each of these doubles eliminators is that they are mounted to the seed meter housing. As a result, there can be significant tolerance stack up between the location of the functional features of the doubles eliminators and the apertures in the seed disk resulting in inconsistent functioning of the doubles eliminator across a plurality of seed meters on the planter.